Users of Microsoft's Windows NT 4.0 Server operating system were reminded Friday that free support will end on December 31 of this year. The move is part of a previously announced program to phase out the aging server software in favor of Microsoft's newer operating systems.

Redmond officials claim that it is not cost-effective for Microsoft to continue supporting NT due to new security vulnerabilities. "These enhancements are included in new platforms such as Windows Server 2003," said Peter Houston, Senior Director of Windows Serviceability. "[They] offer our customers a far greater level of security than is possible with Windows NT Server 4.0."

Microsoft also announced that paid support customers of the operating system will have one extra year to upgrade than previously scheduled. Fee-based support for Windows NT will now cease on December 31, 2006. "Some of our large enterprise and public sector customers have told us they need until 2006 to complete the upgrade," Houston explained.

Paid support customers will continue to receive security updates for NT 4.0; however, these updates will not be made available to the general public.

Microsoft's Houston also said that the company expects to have Exchange Server 5.5 follow a similar phasing-out path starting in 2005.